Site GL157

Location: Gritjurk.

Land Mapping Unit: Dundas Tillite

Australian Soil Classification: Vertic, Mottled-Mesonatric, Grey SODOSOL (confidence level 1).

Site GL157 Landscape.

View towards Bryan Creek from Site GL157.

General Land Unit Description:

This land unit consists of the Permian glacial, fluvial and lacustrine sediment outcrop, in the valleys of the Dundas Tablelands. The landform is mainly dissected low hills and rises. The main soil types occurring in this unit are Black Sodosols or Black Vertosols. Grey Sodosols commonly occur on the lower slopes. This land unit is highly susceptible to water erosion, due mainly to the deep sodic soils. As the Tillite is a mixture of materials (not totally consolidated) the soils (particularly the grey soils) tend to be less stable when exposed. Land slips are common in this land unit.

Site Description:

This site occurs on the Dundas Tablelands. It is situated on a colluvial fan below a rise, leading to a broad alluvial plain. Black clay veins moving through the profile are an indication of the cracking nature of the soil. The internal drainage of the soil is imperfectly to poorly drained. The subsoil becomes considerably more sodic at depth, which may be a cause of the impeded internal drainage. There would be significant run-off accumulating on the site from the dissected tablelands above. The topsoil at this site may be the result of more recent accumulation. On some of the steeper slopes of the Merino Tablelands, relic soil slumping is evident, and the slopes are still susceptible to landslips.

Slope: 4%
Geology: Permian tillite.
Landform Pattern: Undulating rises.
Position in Landscape: Lower slope.
Internal Drainage: Imperfectly to poorly drained.

Soil Profile Morphology:

Surface Soil

A1	0-20 cm	Dark brown (7.5YR3/2); heavy clay loam; fine red (2.5YR4/6) oxidised root channel mottling common; strong very fine sub-angular blocky structure; weak consistence (moist); pH 5.8; clear change to:	Site GL157 Profile.
Subsoil
B21	20-35 cm	Very dark grey (7.5YR3/1); medium heavy clay; many faint fine brown mottles (7.5YR4/4); moderate fine blocky structure; very firm consistence (dry); very plastic when wet; pH 6.2; gradual change to:
B22	35-55 cm	Very dark greyish brown (10YR3/2); medium heavy clay to heavy clay; many fine distinct brown mottles (7.5YR4/4); moderate fine blocky structure; very firm consistence (dry); very plastic when wet; black veins evident due to cracking; pH 6.8; gradual change to:
B23	55-75 cm	Very dark grey (2.5Y3/1); medium heavy clay; fine distinct light olive brown mottles common (2.5Y5/4); moderate to strong structure; very plastic when wet; black veins evident due to cracking; pH 7.8; gradual change to:
B24	75-90 cm	Dark grey (2.5Y4/1); heavy clay; a few faint fine yellow mottles; moderate to strong structure; black veins evident due to cracking; pH 8.5; gradual change to:
B25	90-145 cm	Light olive brown (2.5Y5/3); heavy clay to medium heavy clay; moderate coarse prismatic structure; consistence strong when dry to very firm when wet; very few fine calcareous flecks; black veins evident due to cracking; gradual transition to:
C	145-155 cm	Brown (7.5YR4/4); heavy clay; black veins evident due to cracking.

• Cracking clay subsoil.

Horizon	Horizon Depth (cm)	pH (water)	pH (CaCl2)	EC 1:5	Exchangeable Aluminium mg/kg	Exchangeable Acidity meq/100g	Exchangeable Cations
							Ca	Mg	K	Na
							meq/100g
A1	0-20	5.8	4.6	0.10	62	17	3.7	5.4	0.36	1.5
B21	20-35	6.2	5.0	0.12	15	15	6.2	11	0.69	2.8
B22	35-55	6.8	5.6	0.17		11	7.1	13	0.81	3.7
B23	55-75	7.8	6.9	0.38			7.3	15	1.1	5.7
B24	75-90	8.5	7.8	0.83			7.9	18	1.0	8.0
B25	90-145	8.6	5.5	0.79			6.3	14	0.6	7.1

Horizon	Horizon Depth (cm)	Field Capacity pF2.5	Wilting Point pF4.2	Coarse Sand (0.2- 2.0 mm)	Fine Sand (0.02- 0.2 mm)	Silt (0.002- 0.02 mm)	Clay (<0.002 mm)
A1	0-20	39	19	10	16	27	41
B21	20-35	43	24	5	5	5	61
B22	35-55	47	24	10	9	9	62
B23	55-75	47	25	20	19	20	64
B24	75-90	48	24	61	62	64
B25	90-145